1. Field of the Invention
The present invention generally relates to spray booths. More specifically, the invention relates to air handling in connection with a paint spray booths.
2. Description of Related Art
Many industrial processes require the application of fluid to a material. For instance, applying a surface coating (e.g. paint) to an object requires fluid, such as a liquid or powder slurry, to be sprayed or otherwise delivered to the material. Typically, this fluid application will occur in a contained environment that enables control of the fluid. For example, paint is often applied in a paint spray booth that allows control of the atmospheric conditions and containment of the paint. Inherent in the paint spraying process is overspray. Overspray is paint that does not adhere to the object being painted and floats in the air as a mist. In order to provide a safe working environment and a high quality finished product, paint spray booths require a substantially continuous supply of clean, fresh air. This clean, fresh air also assists with discharge of the overspray from the spray booth.
Various configurations of spray booths have been developed for different fluid application processes and discharge of the overspray. These booths are often classified by the direction of the airflow in the spraying area. For instance, cross-draft booths include an airflow that moves parallel to the floor from behind the operator toward a dry filter or a water curtain. Downdraft booths have an airflow which moves from the ceiling vertically downward to an exhaust system located below the floor. Semi-downdraft booths include an airflow that moves in a diagonal direction in the booth towards an exhaust.
Since the overspray or paint mist contains paint particles, it is important to filter or otherwise clean this air before discharging it back into the environment. Several methods have been developed for separating the paint mist from the air exhaust stream. For instance, a dry method results in air entrained with paint being forced through a dry filter or screen that absorbs or otherwise captures the paint particles. A wet method requires the air entrained with paint to contact and be mixed with another fluid, such as water, so that the paint particles are captured by the fluid.
Due to the large amount of paint used by most industrial paint facilities, such as automotive plants, the wet method in a downdraft booth is the preferred configuration. These booths generally have a wet scrubber that captures the fluid overspray and assists with separating the paint particles from the air.
Over time, various configurations of wet scrubbers have been developed in an attempt to increase the efficiency of the particle separation and to minimize operating costs for the paint facility. Such systems have included gravity based systems where paint laden airflow is made to pass through a bulk liquid, downwardly spilling systems where the airflow passes through a film formed from the liquid, spray systems where the airflow passes through a spray of the liquid and restriction systems where the airflow and the liquid pass through a restriction or Venturi to accelerate the air, generate turbulence, and break-up the supply water (or the capturing fluid) running along its walls. With the latter system, the water is broken-up into small drops that capture or trap the paint particles in the exhaust air within the droplets. Another type of wet scrubber utilizes an elongated tube whereby water flows downward along the walls of the tube and into a pool of liquid contained within a capturing chamber. A nozzle is positioned at the tube's exit to generate turbulence in both the water flow and exhaust air, resulting in the paint particles in the air being captured or trapped within the water.
Still other scrubber designs may utilize a vortex chamber, alone or in combination with one of the other types of scrubbers. In a vortex chamber, the particle laden air flow is introduced into a vortex chamber, follows a spiral path to the center of the chamber where it proceeds upward and out of the chamber. The paint particles are capture by water that is either sprayed outward within the vortex chamber or introduced to the airflow in a Venturi type scrubber system before introduction of both the air and the water into the vortex chamber. The spiral path within the vortex chamber causes the heavier paint laden water droplets to slow along the exterior of the vortex chamber and collect at the bottom thereof, where they are removed. Like the venturi and tube scrubbers mentioned above, scrubbers utilizing vortex chambers of the previously discussed style also have an extensive height and therefore require a significant depth beneath the paint spray chamber.
Although these designs capture and separate some of the paint particles from the air, they use a large amount of energy and/or allow a sub-optimal amount of paint particles to pass through the system and be exhausted to the outside air. Additionally, each of the above style of scrubbers have an extensive height and therefore require a significant vertical depth beneath the paint spray chamber.
A paint spray system that might incorporate the previously mentioned types of wet scrubbers is generally shown in FIG. 1. As seen therein, the under section U beneath the spray chamber C requires a significant vertical height to accommodate a scrubbers S of the above mentioned variety. An under section U may therefore have a height of about 11′3″, as identified in the FIG. 1, while the vertical height from the floor grating of the spray chamber may be about 14′9″, and the vertical height from the floor grating of the spray chamber to a wet floor associated with the scrubber may be about 3′6″. The above recited dimensions are typical and only provided for illustrative purposes and to provide some context in connection with the vertical needed beneath the spray chamber C in order to accommodate a wet scrubber S. In actual practice, these heights may be more or less than those recited, although not drastically different, particularly with regard to being less.
The vertical height required for the under section significantly contributes to the overall cost of the paint spray booth. Additionally, an older system is being retrofitted may require significant digging costs to enable the retrofit.